The present invention relates to water-activated, deferred-action batteries and to a method for producing a cathode for such batteries.
More particularly the present invention relates to a deferred-action battery which is adapted to be activated by immersing it in water. Such batteries may be used for automatically powering emergency lamps and sirens on life-jackets and in case of flooding, for example.
Deferred-action batteries have been known for decades, and various embodiments of such batteries and methods for the production and use thereof, as well as for the manufacture of their component parts, have been described, inter alia, in U.S. Pat. Nos. 2,491,640; 2,636,060; 2,655,551; 2,658,935; 2,716,671; 2,817,697; 3,343,988; 3,859,136; 3,953,238; 4,016,339; 4,192,913; 4,261,853; 4,332,864; 4,368,167; 4,487,821; 4,803,135; and 4,822,698.
As described, for example, in U.S. Pat. No. 2,491,640, batteries of this type are intended especially for use in operating an emergency signal at sea. The signal may be a light to indicate the presence of a person who has become stranded by shipwreck or other causes. It may also be an electronic apparatus floating on the water and emitting a signal which can be detected at a distant point. The battery is adapted to energize the signal and to be activated by immersion in water, which may be the fresh water of an inland lake or river, or the salt water of the ocean.
Such batteries essentially comprise an anode which is usually a magnesium alloy, and a cathode that has traditionally been a silver or copper halide, wherein discharge of the stored energy is initiated by immersing the battery in seawater, which serves as a conducting electrolyte between the anode and the cathode.
Most of the older patents that relate to batteries of this type describe the use of cathodes based on cuprous chloride, while more recent patents such as U.S. Pat. No. 4,192,913 and U.S. Pat. No. 4,261,853 describe cathodes based on cuprous thiocyanate.
U.S. Pat. No. 5,424,147 to Khasin et al, describes a water-activated, deferred-action battery having a housing containing at least one cell, comprising at least one anode selected from the group consisting of magnesium, aluminum, zinc and alloys thereof; a cathode comprising a skeletal frame including conductive metal and having a portion of its surface area formed as open spaces, and further comprising a heat-pressed, rigid static bed of active cathode material encompassing the skeletal frame, the cathode material being formed of cuprous chloride, sulfur, carbon and a water-ionizable salt and being compacted and fused under pressure and heat to itself and to the skeletal frame, to form a heat-fused, conductive, electrochemically active phase; at least one cavity separating the cathode and the at least one anode, and at least one aperture leading to the at least one cavity for the ingress of an electrolyte-forming, aqueous liquid.
Other cathodes described in the Literature have as active material, Copper Sulfate, Lead Chloride, Copper Iodide, Lead Oxide or Potassium Persulfate.
All of the above materials suffer from one or more of the following problems: Sensitivity to humidity upon storage resulting in expansion of the cathode on storage until the cavity between the anode and cathode no longer exists, fast dissolution in water upon activation which results in early failure and high cost. Many use toxic materials.